| Rotating packed bed(RPB)is an efficient mass transfer and molecule mixing equipment designed by the principle of high gravity technology.The centrifugal acceleration inside RPB is hundreds to thousands times of gravitational acceleration through the rotating packing with high speed.When the liquid enters the packing zone,it will be sheared into a large number of liquid micro elements under the huge shear force,resulting in a rapidly renewed interface,which strengthened the gas-liquid mass transfer efficiency and micro mixing performance in RPB.The liquid flow pattern in the packing zone of RPB is closely related to the mass transfer performance of the reactor,which has attracted attention of researchers.At present,it is generally recognized that the main flow pattern in the packing zone of RPB are pore flow,film flow,and droplet flow.With the increase of the rotational speed,the proportion of droplet flow increases gradually.Therefore,the contribution of droplet flow to mass transfer effect of RPB can not be ignored.However,the impacting phenomenon and dispersion mechanism between droplet and wire mesh packing has not been revealed.Therefore,this work mainly studies the liquid flow behavior of droplets impacting on the rotating single-layer stainless steel wire mesh.The dispersion phenomenon of droplets impacting on the rotating single-layer stainless steel wire mesh was photographed by a high-speed camera,and the liquid flow pattern,dispersion angle,and average diameter of daughter droplets are analyzed.The effects of operating conditions on droplet dispersion were investigated.The experimental parameters included RPB operating conditions(impacting angle and rotational speed),droplet initial conditions(droplet diameter and velocity)and mesh parameters(mesh number and surface contact angle).The circumferential wetting behavior of droplets on the wire mesh was observed by CFD simulation,and the variation of gas-liquid interfacial area after droplets impacting on the single-layer rotating wire mesh was analyzed.By analyzing the relative velocity between the droplet and the wire mesh,the dispersion mechanism of the droplet impacting the single-layer rotating wire mesh is clarified.The main conclusions are as follows:(1)There are three stages of a typical process of droplet impacting on the rotating single-layer SSM:contacting and cutting,adhering and stretching,shrinking and breaking.The experimental results show that the impacting angle has a significant effect on the liquid dispersion.With the increase of the impacting angle,the dispersion angle and the number of daughter droplets increased significantly,and the average diameter of daughter droplets decreased.At the same time,increasing the rotational speed and the impacting velocity,enlarging the mesh number and contact angle of the wire mesh surface were beneficial to the enhancement of the liquid dispersion.(2)The relative velocity between the droplet and the wire mesh is the main factor to affect the liquid dispersion.The radial relative velocity affects the time of droplet passing through and spreading on the wire mesh,and the tangential relative velocity affects the spreading velocity of the droplet on the wire mesh.When the impact angle increased from 30° to 150°,the radial relative velocity between the droplet and the wire mesh decreased and the tangential relative velocity increased from 0.98 m/s to 6.34 m/s with the rotational speed of 1000 r/min.The circumferential wetting area of the droplet on the mesh greatly increased and the dispersion effect was enhanced.(3)The growth rate of gas-liquid interfacial area was obtained by CFD simulation under different operating conditions.The impacting angle had a significant influence on the growth rate of gas-liquid interfacial area.When the impact angle was 150°,the peak value of the gas-liquid interfacial area increased 5 times compared with that of 30°of impact angle.The increase of rotational speed and impacting velocity also increased the gas-liquid interfacial area. |
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